One goal of medical research on hematopoiesis is to be able to duplicate the process in vitro for treatment of disease. However, a major complication of this process is that the same factors that stimulate cell growth (i.e., interleukins and colony-stimulating factors) also stimulate unwanted cell differentiation. The overall goal of this research is to develop a hollow-fiber device that selectively removes growth factors from cell-culture media. Phase I established the technical feasibility of the approach by demonstrating that antibodies for a specific growth factor, Interleukin-1 (IL-I), could be immobilized in a hollow-fiber device and used to remove greater than 99% of the IL-1 from cell-culture media at a practical rate and capacity. The objective of Phase II is to immobilize antibodies for other important growth factors (GM-CSF, IL-4, TFG-beta, IL-7, and G-CSF) on hollow fibers and to use modules made from these fibers to elucidate the effect of these growth factors on stem cell growth and differentiation. Experiments will be conducted in which selected growth factors are removed from culture and the resulting effect on cell growth and differentiation quantified. In addition, long-term (5- to 7-week) tests of marrow cell cultures will be conducted in which specific inhibitory factors are removed, with the objective being to determine the requirements for stem cell proliferation.